1. Field of Invention
The present invention relates to a cleaning apparatus and the like that cleans a substrate for liquid crystal display, especially to a substrate edge part cleaning apparatus and the like that cleans an edge part of a substrate by wiping with a cloth.
2. Description of the Related Art
Recently, liquid crystal displays have become widespread as a monitor for a computer and as a television screen, and the number of demands for such liquid crystal displays has been on the rapid increase. Under the circumstances like this, there are also strong demands for the quality improvement and the better price of liquid crystal displays. Therefore, it is a very important task to improve mounting quality and a yield in the process of mounting electrical components on a substrate for liquid crystal display.
With a view to improve mounting quality and the like, a terminal setting area of a substrate is cleaned before electrical components are mounted on the substrate for liquid crystal display in order to improve mounting quality and the like. In this way, bad connections of such electrical components and the like are improved.
As for cleaning an edge part of a substrate for liquid crystal display, automatic cleaning apparatuses have been developed that clean such an edge part by wiping the edge part on which terminals are placed with a cloth containing cleaning liquid and the like. In addition, such apparatuses have been proposed as inventions (for example, refer to Reference Document 1: U.S. Pat. No. 3,445,709.)
Such an automatic cleaning apparatus for liquid crystal display is highly efficient in cleaning and is also highly contributed to the improvement in mounting quality. However, the circumstances surrounding such an apparatus are changing. In other words, it is becoming insufficient to meet the performance requirements for recent substrates for liquid crystal displays.
The first reason is that there is a problem that will be described below. Since the mounting density of electrical components is becoming higher, it is required to maintain high cleaning degree of the substrate surface. Nevertheless, insufficient cleaning operations will be performed in due course. This is because cleaning degrees are evaluated according to only an empirical rule although cleaning degree of the substrate surface decreases to a value below the standard value while cleaning operations are repeated over a long time span. As a result, the yield of the end-product deteriorates.
The present invention is conceived in order to solve the above-described problem. A first object of the present invention is to provide a substrate edge part cleaning apparatus that can evaluate cleaning degrees of an edge part of a substrate and a cleaning method performed by the substrate edge part cleaning apparatus.
The second reason is that there is a problem that will be described below. It is required to narrow, as much as possible, the edge part (frame) of a liquid crystal display because no image is displayed there. However, a conventional cleaning apparatus cannot clean such a narrow frame with a sufficient accuracy of position.
Here, as shown in FIG. 1, a substrate for liquid crystal display includes: a glass substrate B having a frame on which electrical components are mounted; and a color filter C that is a little smaller than the glass substrate B.
Also, in order to narrow such a frame, it is required that the glass substrate B be made smaller as much as possible and electrical components be mounted closer to the color filter C as much as possible. By extension, in order to improve mounting quality of electrical components, the frame of a substrate A for liquid crystal display must be cleaned to the closest extent possible to the color filter C with a high accuracy of position.
However, as shown in FIG. 1, a conventional cleaning apparatus determines the positional relationship between the substrate A and the cleaning head E by pressing three pins D that are mounted on the cleaning apparatus on the edge part of the glass substrate B. However, in the case where setting tolerance between the glass substrate B and the color filter C is great, in other words, an example case where the color filter C is displaced from the glass substrate B, that the positional relationship between the glass substrate B and the cleaning head E is determined does not mean that the positional relationship between the color filter C and the cleaning head E is completely determined. Thus, it is difficult to clean the edge part to the closest extent possible to the color filter C. It is possible to clean the edge part having a predetermined width in the glass substrate B. However, if a part of the color filter C is displaced to the edge part, the color filter C is damaged in the cleaning operation.
The present invention is conceived also in order to solve the above-described problem. The second object of the present invention is to provide (a) a substrate edge part cleaning apparatus that can clean the edge part of the glass substrate B to the closest extent to the color filter C even in the case where the color filter C is displaced from a right setting position on the glass substrate B and (b) a substrate edge part cleaning method.